On this topic and other related ones like the Courage spell (has its own thread so don't start here!) I'm currently a little torn on the best way to proceed.
First EditionFirst Edition kept it simple, you had spell card and potion (treasure) cards with the same effects, so although the rules for handling spells and potions themselves vary, the effects are the same.
Courage Spell - Potion of Strength
Rock Skin Spell - Potion of Resilience
Swift Wind Spell - Potion of Speed
Healing Spells - Healing Potion
Later EditionsLater Editions mixed this up a little, I suspect because spell use is more restrictive, need to use an action, can only be used on your turn, can only be used by a spellcaster (granted you could cast on another but then you needed to be able to see / have LOS to them) they decided to try and give them a little extra to compensate but these changes were themselves revised across editions as they introduced potentially overpowered versions (Courage in SE), and/or caused confusion, this topic and the ever growing
Courage spell topic
So I'm torn with my own version, revert back to First Edition principles, or try and work through the later editions principles and plug holes, any thoughts...